Alcohol effects on drivers' speed management: The influence of visual performance and road complexity.

ABSTRACT

OBJECTIVE: The aim of this work is to assess how drivers adapt their driving speed as a self-regulation mechanism when driving under the influence of alcohol (DUIA), and the influence of alcohol consumption, visual performance, road complexity, and personal traits. METHOD: Thirty one volunteers took part in the study. All of them underwent three experimental sessions Baseline (no alcohol), Alcohol 1 (low-moderate dose), and Alcohol 2 (moderate-high dose). Vision was tested by means of contrast sensitivity and retinal straylight. Driving performance was assessed using a driving simulator. The difference between the driving speed and the speed limit was calculated in 10 road scenarios of different complexity. RESULTS: Drivers adapted their driving speed less (i.e., drove faster) in Alcohol 1 condition compared to Alcohol 2 (p = 0.007). This indicate that participants felt more confident under the influence of a low-moderate dose of alcohol. Participants with better contrast sensitivity drove faster (p = 0.021). The complexity of the road and other factors such as driving experience, gender, or DUIA frequency, also influenced speed choice. CONCLUSIONS: Drivers under the influence of a low-moderate dose of alcohol seem to be less aware of the risk. Contrast sensitivity is a good predictor of the speed choice when DUIA. A better understanding of drivers' behavior under the influence of substance use may be useful to adjust and improve the traffic laws and driving regulations.